Optical navigation systems detect relative movements between the optical navigation systems and navigation surfaces to perform tracking operations. An optical navigation system uses a light source, such as a light-emitting diode or a laser diode, with an illumination lens and an image sensor with an imaging lens to successively capture frames of image data of a navigation surface. The optical navigation system compares the successive frames of image data and estimates the relative movements between the optical navigation system and the navigation surface based on the comparison between the current frame of image data and a previous frame of image data. The optical navigation system is able to track the relative movements between the optical navigation system and the navigation surface by continuously capturing and comparing frames of image data. Optical navigation systems are commonly used in optical computer mice to track the lateral movements of the mice relative to the navigation surfaces on which the mice are manually manipulated.
In some optical navigation systems, the angle of incidence for the illumination light from the light source at the navigation surface is greater than zero with respect to the normal to the navigation surface. Thus, the angle of specular reflection is also greater than zero with respect to the normal to the navigation surface. In these optical navigation systems, the imaging lens is tilted to the angle of specular reflection in order to capture the maximum amount of specular reflection. However, for ease of manufacturing, the image sensor is not tilted to be parallel to the imaging lens. That is, the light receiving surface of the image sensor is not perpendicular to the optical axis of the imaging lens. For such orientation of the image sensor relative to the imaging lens, there are two significant drawbacks that will degrade the tracking performance of the optical navigation system. The first drawback is that modulation transfer function (MTF) across the field of view will not be even due to the field tilt. The second drawback is that distortion will be significantly high.
Thus, there is a need for a system and method for performing optical navigation with enhanced MTF and reduced distortion.